Hollow-core floor slabs

ABSTRACT

The instant invention pertains to various hollow-core slabs used, for example, in various construction applications. The slabs usually include a body with upper and lower shelves joined by two or more substantially vertical ribs and cavities extending longitudinally through the slab body. Two or more reinforcements extending longitudinally through the respective upper and lower shelves of the slab body may be present along with two or more reinforcements extending laterally between the upper and lower longitudinal reinforcements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to Ukraine utility model No. 86140, filed Jul. 25, 2013 and Ukraine utility model 86956, filed Aug. 23, 2013 both of which are incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to the construction field and in particular to structural elements, especially, hollow-core floor slabs of buildings and structures for industrial and/or civil purposes.

BACKGROUND AND SUMMARY OF THE INVENTION

Buildings and other structures often need to be constructed to be durable, steady, and long-lasting—particularly in, for example, hurricane and earthquake-prone regions. Many different ways have been employed in attempting to accomplish these purposes. Unfortunately, many such ways are time-consuming, involve cost-prohibitive materials, or are otherwise difficult to implement. What is needed is a new way to accomplish the aforementioned needs.

Advantageously, the present invention provides a new structure that can be employed in construction. The new structure involves a hollow-core slab. Hollow-core slabs are precast slabs of pre-stressed concrete that may used in the construction of floors in homes and multi-story buildings. The precast concrete slabs often have tubular voids extending the full length of the slab, which makes the slab lighter than floor slabs of equal thickness or strength. Other benefits may include high strength and rigidity, increased heat and sound insulation properties, reduced amounts and costs of reinforcing steel and concrete, and reduced construction costs.

In one specific embodiment, the invention pertains to a hollow-core slab comprising: a slab body comprising upper and lower shelves joined by two or more substantially vertical ribs; cavities extending longitudinally through the slab body; two or more reinforcements extending longitudinally through the respective upper and lower shelves of the slab body; and two or more reinforcements extending laterally between the upper and lower longitudinal reinforcements. The lateral reinforcements are selected from coils, elongated wire, cord loops, and combinations thereof.

In another specific embodiment, the invention pertains to a hollow-core slab comprising: a slab body comprising upper and lower shelves joined by two or more substantially vertical ribs; cavities extending longitudinally through the slab body; two or more reinforcements extending longitudinally through the respective upper and lower shelves of the slab body; and two or more reinforcements comprising wire or cord coils wound along lengths of the upper and lower longitudinal reinforcements and extending laterally between the upper and lower longitudinal reinforcements.

In another specific embodiment, the invention pertains to a hollow-core slab comprising: a slab body comprising upper and lower shelves joined by two or more substantially vertical ribs; cavities extending longitudinally through the slab body; two or more reinforcements extending longitudinally through the respective upper and lower shelves of the slab body; and one or more reinforcements comprising substantially vertically elongated wire or cord loops along lengths of the upper and lower longitudinal reinforcements and extending laterally between the upper and lower longitudinal reinforcements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an end view of an embodiment of a hollow-core floor slab.

FIG. 2 illustrates a side view of an embodiment of a hollow-core floor slab.

FIGS. 3A-B illustrate side views of embodiments of lateral reinforcements.

FIG. 4 illustrates an end view of an embodiment of lateral reinforcements.

FIG. 5 illustrates a cross-section view of an embodiment of a hollow-core floor slab having lateral reinforcements.

FIGS. 6A-B illustrate cross-section B-B in FIG. 5 showing constant pitch of lateral reinforcements.

FIGS. 7A-B illustrate cross-section B-B in FIG. 5 showing variable pitch of lateral reinforcements.

FIG. 8 illustrates cross-section B-B in FIG. 5 showing lateral reinforcements having two coils with mutual displacement by spiral spacing.

FIGS. 9A-B illustrate cross-section B-B in FIG. 5 showing lateral reinforcements with vertical bars between the upper and lower units of longitudinal reinforcements.

FIG. 10 illustrates cross-section C-C in FIGS. 9A-B showing a vertical bar between upper and lower units of longitudinal reinforcements.

FIG. 11 illustrates an embodiment of a hollow-core floor slab, joining the units of lateral and longitudinal reinforcement with a tie wire in places of their intersection.

FIG. 12 illustrates an embodiment of a hollow-core floor slab, joining the units of lateral and longitudinal reinforcement with stirrups in places of their intersection.

FIG. 13 illustrates an embodiment of a hollow-core floor slab, joining the units of lateral and longitudinal reinforcement by twisting the lateral reinforcement in the place of its intersection with the longitudinal reinforcement units.

FIGS. 14A-1, 14B-1 and 14C-1 illustrate various 3D views of embodiments of the present invention. FIGS. 14A-2, 14B-2 and 14C-2 illustrate various side views of embodiments of the invention.

DETAILED DESCRIPTION

A hollow-core slab is disclosed. The slab may be made of a suitable material. A preferred material is heavy concrete. The specific composition and type of concrete employed may vary depending upon the application and properties desired. Such properties include, for example, strength grade of concrete, freeze-thaw durability and water impermeability. In most applications a concrete may be employed which has an average strength, i.e., resistance to axial compression, of at least about 250, or at least about 300, or at least about 350 kgs/cm². On the other hand, for most applications the average strength, i.e., resistance to axial compression, may be less than about 650, or less than about 600, or less than about 550 kgs/cm². In one particular embodiment the concrete employed has a resistance to axial compression between 30MPa and 40MPa.

The person skilled in the art understands that concrete is often subdivided into the following types B1; B1,5; B2; B2.5; B7,5; B10; B12,5; B15; B20; B25; B30; B40; B50; B55; and B60 and grades ranging from M50 to M800. For purposes of the present invention the preferred types and grades include, for example, B30 (M400) with an average strength, i.e., resistance to axial compression, of about 393 kgs/cm²; or B35 (M450) with an average strength, i.e., resistance to axial compression, of about 458 kgs/cm²; or B40 (M550) with an average strength, i.e., resistance to axial compression, of about 524 kgs/cm². It is also preferable for many applications that the slab meet GOST requirements 9561-91 “Ferroconcrete hollow-core floor slabs for buildings and constructions.” In some applications concrete ribs in hollow-core floor slabs are subject to shear and/or tension. Particularly high tension levels are seen in, for example, in the patent of Russian Federation RU87181, filed Dec. 18, 2008 and published Sep. 27, 2009. This often forced manufacturers of hollow-core floor slabs with ribs but without lateral reinforcement to use concrete with higher resistance and quality in order to provide durability.

The slab may be formed in any convenient manner. For example, it can be formed by being pushed through an extruder, by which the concrete mix is substantially thickened to form a quality slab body. In such cases, the resulting product usually has high functional characteristics. The present invention may be particularly applicable to precast concrete hollow-core floor slabs manufacturing technology. Such technology may use continuous casting method and moving form-casting machine (without a butt-end). The manufacturing may be accomplished in any way including, but not limited to, extruding, pressing with vibration, and/or “sleepforming”. This advantageously allows one to avoid conventional welding used in lateral reinforcement since often welding to seven-wire steel strands is not acceptable.

The hollow-core floor slab usually includes a slab body which may be formed by upper and lower shelves joined by vertical ribs with the formation of longitudinal cavities of circular or any other shape cross section in the slab body. Two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, or even more vertical ribs may be employed depending upon the application, materials, and strength desired. The slab also usually includes longitudinal reinforcements which may be pre-stressed and can include upper and lower elements placed respectively in the upper and lower slab shelves in pairs in the planes of vertical ribs of the slab. Two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, or even more longitudinal reinforcements may be employed depending upon the application, materials, and strength desired.

In one embodiment, class K-7 or equivalent ropes (also sometimes referred to strands or tendons) may be used as longitudinal reinforcements. K-7 is seven-wire steel strands and the like which are useful in pre-stresssed concrete constructions. See, for example, ASTM A 416M, A 886/A886M. The precise type and number of wire strands, as well as, rope diameter may, of course, vary depending upon the application. Suitable rope diameters often may include a diameter of from about 8, or from about 9, or from about 10 up to about 14, or up to about 13, or up to about 12 mm.

A particularly preferred method of making the slabs may include first laying out any longitudinal reinforcing ropes or strands to be employed. Next, the lateral reinforcement is put on, for example, flat spiral, flat ring, or both. The longitudinal reinforcing strand ends are attached to pullers to put the strand under tension and form pre-stressed ropes. Any closely placed flat spirals are usually stretched by a suitable way to the desired length. The longitudinal reinforcement is then joined in a suitable manner. Such manner typically does not include welding. A concrete mix is cast and a slab body is formed The slab body may be formed by suitable extrusion methods such as continuous casting method above and this leads to the formation of the slab longitudinal cavities. The cast concrete mix is then heat treated and the slab is cut to desired length. The cutting may be done in any convenient manner. In one embodiment, a band saw is employed thereby cutting the hardened concrete with reinforcement ropes to obtain the finished products with a given length.

Two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, or even more reinforcements extending laterally between the upper and lower longitudinal reinforcements may be used. The actual number of reinforcements will depend upon the application, materials, and strength desired. Lateral reinforcements may be made of any suitable material and configured in any suitable shape both of which may vary depending upon the desired application. In one embodiment, the lateral reinforcements are made of a flexible reinforcement wire or cord. The lateral reinforcements may be put on, for example, each pair of the upper and lower units of longitudinal reinforcement along the transverse ribs of the slab. Alternatively, lateral reinforcements may be configured in the form of, for example, closed vertically elongated separate loops. Such loops can be made of a reinforcement wire or cord and put on each pair of the upper and lower units of longitudinal reinforcement along the transverse slab ribs. The closed loops of lateral reinforcement may be placed along longitudinal reinforcement units with either a constant or a variable pitch.

In one embodiment, lateral reinforcements are only placed on the weight bearing areas of the slab. These areas may vary depending upon the slab shape but generally are the slab ends.

Lateral reinforcements may further include vertical rods, installed between the upper and lower units of longitudinal reinforcement in the planes of vertical ribs. The units of longitudinal and lateral reinforcement in places of their intersection may be joined with any suitable material including, for example, tie wire and/or stirrup, or by simply twisting the lateral reinforcement in the place of its intersection with the longitudinal reinforcement units.

FIG. 1 illustrates an embodiment of a hollow-core slab including a slab body with lateral and longitudinal reinforcements. The slab body is formed by the upper 2 and lower 3 shelves which are joined by vertical ribs 4 with the formation of longitudinal cavities 5 in the slab body. Longitudinal reinforcement comprises the upper 6 and lower 7 units, which are placed in the upper 2 and lower 3 shelves of the slab respectively. The upper 6 and lower 7 units of longitudinal reinforcement are placed in pairs in the planes 8 of vertical ribs 4 of the slab. The longitudinal reinforcement units 6, 7 may be pre-stressed. This may reduce the amount and associated cost of reinforcing steel while preserving the load-bearing capacity of a slab. FIG. 2 illustrates a side view of the slab body and points of potential failure along line 1 in the absence of using lateral reinforcements as described herein.

FIGS. 3 and 4 illustrate embodiments of lateral reinforcements. Shown in FIGS. 5-7, lateral reinforcements may be configured in the shape of coils 9, which are made of a flexible reinforcement wire or cord and put on each pair of the upper 6 and lower 7 units of longitudinal reinforcement along the transverse ribs 4 of the slab. Alternatively, lateral reinforcements may be configured in the form of closed vertically elongated separate loops 9 which are made of a reinforcement wire or cord and put on each pair of the upper 6 and lower 7 units of longitudinal reinforcement along the transverse slab ribs 4. Shown in FIGS. 6 and 7, lateral reinforcements may be placed on the marked pairs of longitudinal reinforcement units 6, 7 with each having either a constant or variable pitch. This allows one to selectively increase the slab's bearing capacity and reliability of exploitation to the required size. In one embodiment, lateral reinforcements may be placed only on the slab ends, which allows one to increase the strength of the slab on its bearing areas which often include the slab ends. FIG. 8 illustrates a cross-section view of lateral reinforcements having two coils with mutual displacement by spiral spacing.

FIGS. 9 and 10 illustrate vertical rods 10 associated with lateral reinforcements, installed between the upper 6 and lower 7 units of longitudinal reinforcement in the planes 8 of vertical ribs 4. These advantageously fix the distance between the upper 6 and lower 7 units of longitudinal reinforcement, perform additional functions of lateral reinforcement, and/or which may further increase the load-bearing capacity of the slab.

FIGS. 11-13 illustrate longitudinal reinforcement units 6, 7 and lateral reinforcement closed loops 9 in places of their intersection, which may be joined with a tie wire 11 (FIG. 11), or stirrups 12 (FIG. 12), or by twisting 13 lateral reinforcement closed loops 9 in places of their intersection with the longitudinal reinforcement units 6, 7 (FIG. 13). As a result, there is a reinforcing cage which provides the given load-bearing capacity of the slab and exploitation properties with minimum costs of reinforcing steel.

There are many methods of making the slabs of the present invention. In one method hollow-core floor slabs are made by first pre-producing billets of lateral reinforcement (FIGS. 3-4) in the form of closed vertically elongated separate loops 9. In one embodiment, the form and dimensions of the lateral reinforcement allows one to place the billets on the corresponding pairs of longitudinal reinforcement units 6, 7, with the formation of linear vertical areas of lateral reinforcement between longitudinal reinforcement units 6, 7 put on lateral reinforcement closed loops 9. The billets 9 are then put on longitudinal reinforcement units 6, 7 and placed along the vertical ribs 4 with constant or variable pitch.

Next, continuous undecked formation of hollow-core floor slabs is undertaken. The units 6, 7 are subjected to pre-stress the amount of which may vary depending upon the application. The pre-stressed longitudinal reinforcement units 6, 7 are placed in the slab shelves 2, 3 and lateral reinforcement closed loops 9 are placed in the vertical slab ribs 5. The slab body is formed by extrusion which results in the formation of longitudinal slab cavities 5. The cast concrete mix is heat-treated and the received slab billet is cut by, for example, cutting the hardened concrete with longitudinal and lateral reinforcement with a band saw to the desired finished length. The result are hollow-core floor slabs with pre-stressed longitudinal reinforcement units placed in the upper and lower slab shelves and with lateral reinforcement units placed in vertical ribs of the slab.

Advantageously, hollow-core slabs with lateral reinforcements configured as closed vertically elongated separate loops put on each pair of the upper and lower units of longitudinal reinforcement along the slab vertical ribs may provide an increase in the carrying ability of bearing areas of the slab and/or reliability of its exploitation in case of fire or corrosion damage. The lateral reinforcement of a slab performed in the aforementioned way perceives transverse tensile stress and prevents a possible emergency destruction of the slab, for example, along the line 1 shown in FIGS. 1 and 2. Providing lateral reinforcements in the form of closed vertically elongated separate loops put on each pair of the upper and lower units of longitudinal reinforcement along the slab vertical ribs facilitates the connection of longitudinal and lateral reinforcement units without performing welding works. Such welding is often not desirable and often avoided when using pre-stressed reinforcement. Moreover, such lateral reinforcements increases the bond between longitudinal reinforcement and concrete. This may be beneficial in cases of delamination of the protective layer of concrete in case of fire or corrosion damage. The lateral reinforcement performed in the form of closed loops, which enfold the longitudinal reinforcement units and which are placed in the planes of the slab vertical ribs, usually does not prevent the formation of the slabs using the technology of continuous extrusion formation of finished products. The lateral reinforcement in this form also provides effective anchorage of lateral reinforcement and/or transverse tensile stress. The lateral reinforcement in this form also may facilitate a bond between longitudinal reinforcement and concrete. Advantageously, the design is fully consistent with the existing standards of projecting reinforced concrete constructions, cost-effective, and/or efficient. Thus, the embodiments of the present invention may usually be employed in any building where currently known hollow-core floor slabs are employed.

The claimed subject matter is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the invention in addition to those described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are intended to fall within the scope of the appended claims. 

What is claimed is:
 1. A hollow-core slab comprising: a slab body comprising upper and lower shelves joined by two or more substantially vertical ribs; cavities extending longitudinally through the slab body; two or more reinforcements extending longitudinally through the respective upper and lower shelves of the slab body; and two or more reinforcements extending laterally between the upper and lower longitudinal reinforcements and wherein said reinforcements are selected from coils, elongated wire, cord loops, and combinations thereof.
 2. The slab of claim 1, wherein the lateral reinforcements comprise coils wound around the upper and lower longitudinal reinforcements.
 3. The slab of claim 1, wherein the lateral reinforcements comprise substantially vertically elongated wire or cord loops wound around the upper and lower longitudinal reinforcements.
 4. The slab of claim 1, wherein the longitudinal reinforcements are substantially coplanar with the substantially vertical ribs in the slab.
 5. The slab of claim 1, wherein the lateral reinforcements comprise either a constant or variable pitch along the longitudinal reinforcements.
 6. The slab of claim 1, further comprising substantially vertical rods, installed between the upper and lower longitudinal reinforcements, wherein the rods fix the distance between the upper and lower longitudinal reinforcements.
 7. The slab of claim 6, wherein the substantially vertical rods are substantially coplanar with the substantially vertical ribs in the slab.
 8. The slab of claim 1, further comprising one or more tie wires for securing lateral reinforcements at one or more locations where said lateral reinforcements intersect with said longitudinal reinforcements.
 9. The slab of claim 1, further comprising one or more stirrups for securing lateral reinforcements at one or more locations where said lateral reinforcements intersect with said longitudinal reinforcements.
 10. The slab of claim 1, wherein lateral reinforcement loops are twisted at one or more locations where said lateral reinforcements intersect with said longitudinal reinforcements.
 11. The slab of claim 1, wherein lateral reinforcements are located proximate ends of the slab body.
 12. The slab of claim 1, wherein the longitudinal reinforcements are pre-stressed.
 13. A hollow-core slab comprising: a slab body comprising upper and lower shelves joined by two or more substantially vertical ribs; cavities extending longitudinally through the slab body; two or more reinforcements extending longitudinally through the respective upper and lower shelves of the slab body; and one or more reinforcements comprising wire or cord coils wound along lengths of the upper and lower longitudinal reinforcements and extending laterally between the upper and lower longitudinal reinforcements.
 14. The slab of claim 13, wherein the wire or cord coils are configured having either a constant or variable pitch along lengths of the longitudinal reinforcements.
 15. The slab of claim 13, further comprising substantially vertical rods, installed between the upper and lower longitudinal reinforcements, which fix the distance between the upper and lower longitudinal reinforcements.
 16. The slab of claim 15, wherein the substantially vertical rods are substantially coplanar with the substantially vertical ribs in the slab.
 17. A hollow-core slab comprising: a slab body comprising upper and lower shelves joined by two or more substantially vertical ribs; cavities extending longitudinally through the slab body; two or more reinforcements extending longitudinally through the respective upper and lower shelves of the slab body; and one or more reinforcements comprising substantially vertically elongated wire or cord loops along lengths of the upper and lower longitudinal reinforcements and extending laterally between the upper and lower longitudinal reinforcements.
 18. The slab of claim 17, wherein the substantially vertically elongated wire or cord loops comprise either a constant or variable pitch along lengths of the longitudinal reinforcements.
 19. The slab of claim 17, further comprising substantially vertical rods, installed between the upper and lower longitudinal reinforcements, which rods fix the distance between the upper and lower longitudinal reinforcements.
 20. The slab of claim 19, wherein the substantially vertical rods are substantially coplanar with the substantially vertical ribs in the slab. 